/**

* @function countSubstrings

* @description Given a string of words or phrases, count the occurrences of a substring

* @param {String} str - The input string

* @param {String} substring - The substring

* @return {Number} - The number of substring occurrences

* @example countSubstrings("This is a string", "is") => 2

* @example countSubstrings("Hello", "e") => 1

*/

const countSubstrings = (str, substring) => {

if (typeof str !== 'string' || typeof substring !== 'string') {

throw new TypeError('Argument should be string')

}

if (substring.length === 0) return str.length + 1

let count = 0

let position = str.indexOf(substring)

while (position > -1) {

count++

position = str.indexOf(substring, position + 1)

}

return count

}

export { countSubstrings }